Drill bit



July 9, 1940.

A. ZUBLIN DRILL BIT Filed Jn. 25, 1959 fof/N A. ZuL/N,

Patented July 9, 1940 A UNITED sTATEs PATENT ori-Ica y This invention relates to drill bits, being particularly concerned with the cooperation between a drill bit bearing and a cutter rotatably mountedfthereon. More specicaily, the present in- 5 vention. is an improvement on the drill bit described in the patent of John A. Zublin, No. 2,025,259, granted December 24,1935.

In the patent referred to, the cutter is mounted on a shank bearing to rotate about an axis l inclined with respect to the axis of the bit. The

cooperable bearing surfaces on the cutter and taken along the plane 2,-2 of Figure 1;.

shank include a cylindrical portion designed to transmit radial loads, and a terminal frusto.

conical portion designed to transmit substantial.- l5 ly the entire axial thrust and also to center the 'cutter with respect to the shank. -Under many conditions ofv operation, proper bearing relationship between the cutter and shank bearing is maintained, with the cutter in contact with large peripheral areas on both'the cylindrical uand frusto-conical surfaces of the shank bearing.

These large contact areas resultr in low unlt'bearv ing pressures and a consequent long life ofthe bearing surfaces on both the shank and cutter. But under vsome conditions of operation, the cut-r ter tends to tilt or cock with respect to the shank bearing surfaces and their inclined axis,

altering the bearing cooperation between the cutter. and shank from one in. which large surfaces 3 0 are in contact to one in which only point or relatively small areas are in contact. 'Ihe latter condition is attended with high unit vbearing pressures and a consequent short useful life of the bearing surfaces on both the shank and cutter.

Accordingly, it is an -object of the present in- -yention to minimize or eliminate the tendency of a roller cutter to tilt or cockon its supporting e bearing, thereby maintaining large areas of the 40 bearing surfaces in contact, and eiecting an increase in the useful life of the bit as a whole.

Another object of the invention is to provide a drill bit foroil wells and the like having a I bearing construction servingi to center the cutter on the bit shank, and in which the cutter is `held centered on the shank by its production; while in operation, of 'an additional generally ra-` dial bearingsurface on the shank bearing.

A further object of the invention is to provide improved means for lubricating the bearings of drill bits.

This invention posessess many other advantages and has other objects that will become ap'- parent from a consideration of an embodiment ofthe invention. For this purpose, a .form is *defined by the appended claims. Y

conical portion I1. bearing for the cutter is made of two physically trating the general principles of the invention.

However, it is to be understood that this de- '5 tailed description is not to be taken in a limited sense, since the scope of the invention is best Referringto the drawing: Figure 1 is a side elevation of a drill bit; 10 Figure 2 is a section, on an enlarged scale,

Figure 3 is a. transverse section taken along the plane 3-3 of Figure 1;

Figure 4 is a diagrammatic view showing the 15 lmanner m which e cutter tends tc maar cock `-closed including a shank Ill having a tapered threaded pm n at its upper end f dr attaching 26 the bit to a string of drill pipe (not shown) .e The bottom of the shank terminates in a bearing I2 for a cutter whose axis A-A is inclined.- to the shank axis B-B by an angle .'c. A cutter I3 is mounted on the bearing for rotationfabout theA axis AA, and comprises a bowl-shaped body, the internal surfaces of which are complementary to the outer faces of the lshank bearing. lower end of the shank is finished to form-'a cylindrical portion Il of generally uniform diameter. This 36 cylindrical portion threadedly receives a thrust cone or pin I5, whose -outer surfaceincludesa cylindrical portion I6 of' substantially-'the same diameter as the cylindrical portion on the shank` and a terminal, downwardly disposed frusto- 40 Despite the fact vthat the separable members, it is essentially asngle unitary bearing having a cylindrical surface merging or continuing into'a frusto-conical portion. 45

As a large part of the bearing wear occurs onv the thrust cone =surfaces, it is preferred ,to make the cone or pin I5 removablefrom the remainder of the-shank, although it is to be understood that the complete 'bearing could be made in one |50 piece, if desired. As aforementioned, the internal'bearing'sur-- faces I8, vIii on the bowl-shaped cutter are complementary and engageable with the correspondingcyundricaiand frusta-comcaisurfcces zum, aus

' -22 on the shank and its thrust cone. This cutter is held against removal from the shankby a plurality of balls or other bodies 23 rollable in a peripheral groove 24 forrnedel in the shank bearing, and also within a peripheral groove or recess 25 formed in the interior of the bowlshaped cutter. These balls 23 are preferably somewhat less in diameter' than the total radial distance across the ball channels 24, 25 so that the balls do not act as bearings, the cutter receiving its support directly from the shank and its thrust cone or pin. It is to be understood, however., that these balls, or their equivalent, could also function as anti-friction bearing members, if desired. f

The balls are introduced into the peripheral grooves 24, 25 through a longitudinally extending recess 2B provided in the cylindrical bearing portion of the shank above its peripheral groove. After a suilicient number of the Aballs have been thus introduced, they are'held in place by a.V

suitable locking plug 21 fitting within the longitudinal recess and held there by meansof a suitable lock screw 28 and an additional safety screw 29., Further details of the locking device can be' found in Patent No. 2,025,259, above referred to.

'Ihe apex angle p of the truste-conical thrust pin l is preferably such" with respect, to the extent of inclination of the axis A-A to the axis B-B that the lowermost cone surface makes an acute angle q with the shank axis B--B. Be-

cause of this arrangement, the cutter tends to be self-centered on the frusto-conical bearing in view of longitudinal `components of thrust between theformation and the cutter having a component tending to slide the cutter upwardly on its supporting bearing. Under many conditions of operation, this self-centering action'pro- I vides a large surface of bearing contact between the frusto-conical portions of both the piri I5 and cutter I3. 'I'his is true of the arrangement result, surface bearing contact is lost betweenl the cutterand the cylindrical and frusta-conical portions of the shank. Localized wear then oc- 1 curs on the cylindrical shank 4bearing portion r above the peripheral ball groove 24, primarily in the quadrant region designated by the angle s in Figure 3. Substantially diagonally opposite this region of localized wear, tilting of the cutter Y moves its frusto-conical surface 1,9 over the smaller frusto-conical base 30 of the pin (see Figure 4). VSubstantially point bearing contact t, instead of ,'the desirable surface bearing conf tact, occurs between the smaller base portion of surfaces.

the-pin I. and the sides *I9 of the cutter, producing exreme localized `wear on the cone i5 and also tending to cut a groove upon the tapered cutter bearing surface as it rotates with respect to the shank. The extent of cone wear can be decreased somewhat by hardfaclng its bearing But this entails the disadvantage of increasing the extent 'of wear on the cone bearns surfaces i9 of the cutter. As these parts and the cylindrical shank parts r in the quadrant region s wear, the cutter can be tilted still further towards parallelism with the shank axis, aggravating the localized point bearing engage?. ments r, t between the cylindrical and co'nical surfaces on both the shank and cutter.

'I'he present invention overcomes the tilting action of the cutter on its supporting bearing by preventing the cone bearing surface I9 on the cutter from sliding over the smaller, end 30 of the piu, as in Figure 4. This objective is achieved by extending the -cone portion 32 of the pin beyond the smaller base 3i of the cutter frustum. 'I'he degree of this extension need not be large, so long as the cutter is prevented from tilting over the smaller end 33 of the cone, by the engagement of its smaller base portion 3| with the tapered sides 22 of the pin. Under extreme conditions of operation, the terminal cutter portion 3l might tend to dig into-the sides of the cone. .This tendency can be oilset by hardfacing the cone, but in the event that some deformation of the cone does' occur upon upward movement of the cutterv on its bearing, the result will be the production by the rotating cutter of a shoulder 34 at the lower end of the thrust cone (see Figure 5,). The shoulder thus formed will operate in the manner of a radial bearing, tending to prevent tilting of the cutter towards parallelism with the shank axis, and consequently,.oifers assurance ,that surface bearing contact between the cutter andthe inclined shank portions is maintained to a much greater extent than heretofore, the acute angle q that the lowermost cone portion makes with the shank axis still tending to maintain the cutter centered upon the shank bearings.

The bit disclosed in the drawing is provided with the usual water course 35 in the shank com-` municating -with passageways 26, 31 through the inclined shank pin and thrust cone, and

charge drilling fluid against the bottom toremove cuttings therefrom. An additional water nozzle 39 is also threaded into a channel 4l communicating with' the shank water course to direct a stream of iiuid uponthe cutter teeth. In addition, radial side .holes 4| are provided in f the thrust cone extending from the passageway 31 in the-cone to side slots'42 opening upon the bearing. surfaces thereon to permit passage of lubricating fluid to the bearing surfaces. The lpassage 31 through the cone is preferably cylindrical and of uniform dimensions 4throughout its entire length in order to eliminate all restric- 4ISIS tions tothe flow of fluid therethrough tending to buildup back pressures. The side holes 4| to the cylindrical central cone water passage 31,

A'so that any 'abrasive matter passing through the cone will be conveyedv past the side holes in view of their relatively higher density and kinetic energyl permitting only clean drilling` fluid to flow through the side holes tothe bearing surfaces. If any restrictions were present in the central conechannel 31, a back pressure would be built up,'forcing the abrasive matterthrough the side holes 4l. Moreover, if the .side holes extended downwardly and outwardly from the central' g water passage, rather than being at right angles vthrough' the cone are arranged at right angles thereto, or extending upwardly and `outwardly therefrom, the abrasive laden fluid couldv still the abrasive matter to iiow past their entrance openings.

I claim: I A Y 1. In a drill bit, a shankl having a bearing, a bearing pin threaded into said shank bearing, a fluid passageway in the shank communicating with aligned channels in said shank bearing and bearing pin, the channel in said bearing pin being free from `restrictions and having an exit open-` ing at its lower end, said pin being provided with a hole at right angles to the axis of its Achannel which establishes communication between the pin channel and its bearing surfaces, and a cutter rotatably mounted on said pin and shank bearing.

2. In a drill bit, a shank having a cylindrical bearing, a bearing pin threaded into said bear' ing and having a cylindrical bearing surface adjacent said cylindrical bearing and a conical surface, a uid passageway in Athe shank communicating with aligned channels in said shank bearing and bearing' pin, the channel in said bearing pin being free from restrictions and having an exit opening at its lower end, said pin being provided with a hole substantially at right angles to the axis of its channel establishing communication between the pin channelV and its cylindrical bearing surface, and a cutter rotatably mounted on said pin and shank bearing.

3. In a drill bit,v a shank having a cylindrical bearing threadedly receiving a bearing pin having a. cylindrical bearing surface adjacent said cylindrical bearing and a conical surface, a fluid passageway in the shank communicating with passages in` said shank bearing and bearing pin, the pin passage being free from restrictions and having an exit opening at its lower end, a slot in the side of saidpin, said pin being provided with a hole substantially at right angles to the axis ofI its passage establishing communication between the pin passage and slot, vand a cutter rotatably mounted on said pin and shank bearing.

4. In a .drill bit, a shank threadedly receiving a removable bearing pin, a cutter rotatably mounted on said pin, a uid passageway in said shank communicating with a passage through said pin having an exit opening at its lowerend, the pin passage being free from restrictions, said pin having a slot in its vbearing sides, and said pin being provided with a hole substantially at right angles to its passage establishing communicationbetween the pin passage and slot.

JOHN A. ZUBLIN.

1lil 

